The invention is related to the field of hearing aid devices. More particularly, the invention relates to assistive listening devices that bring sound from remote locations directly to the ear to improve signal-to-noise response.
Conventional hearing aids consisting of an integral microphone, amplifier and earphone worn within or partially behind the ear, are based on the principal of providing amplified sound to the hearing impaired individual. Typical hearing aids, however, provide little benefit to individuals having specific hearing difficulties related to distinguishing intelligible sounds from ambient noise conditions. In conditions such as a noisy crowded room, group discussions, and telephone conversations, the hearing aid amplifies the background noise as well as the sounds from the source of interest to the user, the result being unintelligible noise.
In order to overcome the deficiencies of conventional hearing aids, assistive listening devices have been developed that bring signals directly from the source of interest to the ear of the hearing impaired individual. The most common assistive listening device is the telecoil (T-coil) that picks up the electrical fields generated from a telephone receiver and converts the fields to signals supplied directly to the amplifier of the hearing aid. In some cases, the T-coil is incorporated directly into the body of the hearing aid. Other assistive listening devices include the use of microphones that are placed in close proximity to the source of interest, for example a television, and are directly connected to the circuitry of the hearing aid.
The use of assistive listening devices in conjunction with a hearing aid requires that a switching mechanism be provided for switching between the integral microphone of hearing aid and the assistive listening device. This has presented a problem in conventional hearing aids which have been miniaturized in order to reduce their visibility, namely, the switching adjustment controls provided on the hearing aids are so small that they require a good deal of manual dexterity. Also, assistive listening devices that require physical electrical connections between the assistive device and the hearing aid severely limit the users mobility and are very conspicuous. Further, the number of assistive listening devices that can be utilized with the hearing aid is restricted, as they tend to work individually and cannot be combined. Furthermore, emergency messages or other public announcements are not well perceived by the hearing impaired with conventional devices.